Auxiliary boiler



y 1947- I M. c. CROTTY 2,420,231

AUXILIARY BOILER Filed June 13. 1944 s sheets-sheet 1 IN V EN TOR.

BY M/(f/AZZ c. c/mrrr May 6, 1947. CR T 2,420,231

AUXILIARY BOILER- Filed Julie 13, 1944 3 sheets sheet 2 mmvroa Mal/4.5.4 C. C8077) ATTQRMY May 6, 1947 M. c. CROTTY AUXILIARY BOILER s She'ets-Sheet 3 Filed June 13, 1944 mm $N x INVENTOR. AI/Cf/Afl C. 6/?077) .can be Patented at s, 1941 AUXILIARY BOILER Michael C. Crotty,

Flushing, N. Y., assignor to Crotty Manufacturing Corporation,

New York,

N. Y., a corporation of New York Application June 13, 1944, Serial No. 540,085 Claims. (CL 122-4) The present invention relates to steam producing furnaces of the type adapted for use as 'central heating apparatus. More particularly, it relates to a type of furnace that may be used as an auxiliary apparatus in connection with a main furnace to handle extraordinary loads.

The main furnace which may be coal fired is used to handle all normal loads and the auxiliary furnace of the invention is so connected as to be cut in on high peaks. and to be cut out when the load returns to normal. The auxiliary furnace, which preferably.is oil fired, but may use other fuel such as powdered coal or gas, is intended for use in connection with a boiler and the principle of low pressure forced circulation ispmployed.

In applying the invention to low pressure work the furnace proper can be, with advantage, coal fired using ordinary coal grates and coal stokers, while the auxiliary furnace can be oil fired. It is thus possible to operate the same boiler on oil or coal or a combination of both.

Where the furnace proper flredwith coal has been already installed, the auxiliary furnace may be installed in connection therewith. In such a case the ordinary efficiency of the furnace proper will not be impaired, since the only alteration necessary will be a slight shortening of the grate area. If, however, the whole installation is new, or if the combustion gases from the auxiliary furnace pass to the main combustion chamber in the manner hereinafter described, even this change will not be necessary. However, when heating the boiler through the-oil fired auxiliary furnace of the invention, very high efiiciencies attained. In actual practice it has been found possible to increase the emciency of the plant by as much as 50%. This has beenmade possible by the extended firing arrangement of the auxiliary furnace and the use of forced circulation in connection therewith. The invention is particularly useful on boiler loads that are subiect to suddenly increase I. demands.

The auxiliary furnace of the invention has special adaptation to use with, for instance, a furnace of the locomotive boiler type. and it may be installed either at the back of the combustion chamber of such a furnace or in such other position at the sides as convenience and demands of space indicate, and it may be installed above or below the grate level of the coal fired main furnace. Broadly, the invention comprises a pump drawing water from the boiler at one side and forcing it through a series of annular tubes at the other. These annular tubes are connected by headers at top and at bottom, and an oil burner of any conventional type is provided at one end and an opening communicating with the combustion chamber of the main furnace permits the flow of the gases of combusticn into the combustion chamber of the main furnace. A fire brick bridge and bafiie wall may be built into the combustion chamber of the main furnace opposite the exit of the combustion gases from the auxiliary furnace to act as a bafiie directing the flow of such combustion gases so that they eddy upwards and through the tubes of the boiler and at the same time aid in maintaining an adequate depth of the fire bed in the main furnace grates. If the auxiliary furnace, however, communicates with the main combustion chamber above the grate level, this wall may not be necessary. Suit= able connections between the top header of the annular tubes extend upwards and open into the boiler above orbelow the water level. Compensating valve connections are provided at the point where the return. enters the boiler above the water line, and these can be so adjusted as to provide a pressure drop preventing the separation of water and steam until the flow has passed into the boiler. Orifice plates or other pressure drop devices may also be employed for this purpose. The pump is adapted to pass a flow of about fifty gallons per minute or less into the coils so that they are at all times full and so that the steam formed in'the coils is not permitted to separate from the water while in the coils.

The invention will be more clearly understood from the drawings in which Fig. 1 represents a coal-fired locomotive boiler type furnace with the sides partially broken away and with the auxil iary furnace installed, the auxiliary iumace being represented as oil fired and the return pipes being connected to the boiler above water level; Fig. 2 is a rear elevation of the furnace of Fig. 1; Fig. 3 shows the auxiliary furnace; Fig. 4 is the annular tube unit of the auxiliary furnace showing a series of annular tubes connected by top and bottom headers; Fig. 5 shows one of said annular tubes viewed in elevation from the front of the auxiliary furnace; Fig. 6 shows an arrangement of the auxiliary furnace which renders. the bridge or bafiie wall unnecessary; and Fig. 7 is a detail of the compensating valve indicated at it in Figs. 1 and 6.

Referring now to Fig. 1, i is a boiler partially filled with water and having tubes 2 running from the combustion chamber 3 through the water of the boiler to the smoke box 5 through which the gases of combustion flow,

and other tubes 4 also Grates 1 are provided in the combustion chamber 3 of the main furnace which is represented as coal fired, and an ash pit 8 below the grates accommodates the ashes. A fire brick bridge and bafile wall 9 projects within the combustion chamber of the'main furnace above the grate level, facing the exit end of the auxiliary furnace. This auxiliary furnace comprises an oil burner unit ID of any.conventional type, and a series of annular tubes I I. The annular tubes are connected at the bottom by the header l2 and at the top by the header l3. A pipe I 4 connects with the top header l3 and rises to a point above the boiler and then descends to connect therewith. A compensating valve l5 functions both as a pressure drop device and to control the oil burner firing system in the manner more fully described hereinafter. A pump l6 operated by motor l1 connects with the water of the boiler through pipe l8 and hand valve l9, thus, when in operation, drawing water from the boiler and pumping it through pipe 20 into the lower header i2. This pump is arranged to produce a flow of about fifty gallons 2. minute or less.

The auxiliary furnace unit is installed in a housing of cylindrical form comprising the steel sheet covering 2| completely surrounding the furnace and having an insulation lining 22 within the steel sheet and a further lining of refractory material 23 within the insulation lining. A drain pipe 24 controlled by hand valve 25 connects with lower header l2 through which, when it is necessary to clean sediment from the pipes, the auxiliary furnace system can be blown down.

The compensating valve I 5 is shown in detail in Fig. '7. It will be seen that within the valve is an orifice 28-which is covered by a hinged cover 21. Fastened to the hinge of the cover and moving therewith is a mercury switch 28 having an arm or extension 29 which is connected with the spring 30. The tension of the spring 3015 controlled by the nut 3|. Conductors 32 proceed from the mercury switch through suitable connections, not shown, to the firing system of the oil burner Hi. It will be understood that when the cover 21 is closed, the mercury in the switch will lie level and there will be no connection between the conductors 32; but when the pressure within pipe I4 is sufilcient'to lift the cover 21 upwards away from the orifice 28, the mercury switch arm 25! is tipped upward against the pull of the spring 30 and the mercury flowing down within thechamber of the switch forms a connection between the conductors 32 and starts the oil burner l0 into operation. Thus, the spring 30 may be set by turning the nut 3i to produce a tension in the spring suflicient to compensate for a pressure differential of five pounds within the pipe I4 and so long as this pressure differential is not exceeded the valve will be closed and no water or steam'will pass through the orifice 26.

Assuming, however, that a pressure differential in excess of five pounds is developedthe cover 21 will be forced up and the steam and water will be allowed to separate and return to the top of the boiler l.

'4 As will be seen from Fig. 1, the pump it draws water from the bottom of the boiler I through pipe It! at a point about the grate level, and forces it through pipe 20 into the lower header 12, the rate of flow being such that the annular tubes ll, headers l2 and I 3, and pipe I are at all times completely filled with water in. which the steam generated by the heat from the oil burner l0 remains unseparated. However, the compensating valve l5 being opened by the pressure permits steam and water to separate within the boiler above the water level so that a head of steam is built up in the top of the boiler above the water level whence it may be piped off as desired through the outlet 26 at the top of the boiler.

In Fig, 6 a slightly different relation of the auxiliary furnace to the main furnace is shown. In the figure, the auxiliary furnace is shown connected with the combustion chamber of the main furnace at the side through a gooseneck connection 33, though it might equally well be attached in the same manner to the rear as shown in Fig. 1. However, it differs from Fig. 1 in that instead of the auxiliary furnace opening directly into the combustion chamber of the main furnace, the gooseneck passage 33 carries the gases of combustion from the auxiliary furnace upwards and into the combustion chamber above the grate level. With this arrangement, the auxiliary furnace may stand on the floor below the grate level of the combustion chamber of the main furnace, and as the gases of combustion pass into the main combustion chamber at a higher level, a bridge or baille wall such as indicated at 8 in Fig. 1 is unnecessary, and it is likewise unnecessary to shorten the grate area within the main combustion chamber. Also, as shown in Fig. 7, the pipe H which returns the steam and hot water from the top header l3 to the boiler is connected to the top header at both ends through the branching pipe 34. This same arrangement is equally applicable to the furnace arrangement shown in Fig, 1, and,

while the functioning of the furnace is not materially changed thereby, it has the advantage of easing th flow from the top header back to the boiler since water flows into pipe I from both ends of the top headers l3.

Having thus described my invention, what I claim is:

1. In a steam heating system a main furnace combustion chamber, a tubular boiler associated therewith, and a secondary furnace auxiliary to said main furnace, said auxiliary furnace comprising a plurality of annular tubes connected at top and bottom by headers and a,combustion chamber embraced within said tubes; a pipe connection between said bottom header and the water in said boiler and a pump in said pipe connection between said boiler and said bottom header; a second pipe connection between said top header and said boiler above the level of water in said boiler, and pressure drop means at the outlet of said second pipe connection into said boiler; an opening from the combustion chamber of said auxiliary furnace communicating with the-combustion chamber of said main furnace whereby combustion gases from said auxiliary furnace escape into the combustion chamber of said main furnace and heme means within said main furnace opposite the communicating outlet of said auxiliary furnace whereby the gases of combustion escaping from said auxiliary furnace into said main furnace are caused to eddy within said main furnace combustion chamber and to pass through the boiler tubes together with the gases of combustion of said main furnace.

2. A steam heating system according to claim 1 in which said auxiliary furnace is oil tired and said main furnace is coal fired.

3. In a steam heating system, a main furnace combustion chamber, a. tubular boiler associated therewith and an auxiliary furnace having a combustion chamber communicating with said main furnace combustion chamber surrounded by annular tubes adapted and arranged to heat water passing through said annular tubes under forced circulation independently of the water heated by said main furnace and boiler; and 'means by which water is withdrawn from said boiler, forced through said annular tubes and returned to said boiler through a pipe delivering nections; a second pipe connection between said.

top header and said main boiler above the water level, and a compensating valve pressure drop means located adjacent the outlet of said second pipe connection into said main boiler.

5. In a steam heating system according to claim 4, a compensating valve comprising an opening and a hinged cover upon said opening; a mercury switch external to said valve v.ailixed to said hinged cover and moving therewith, whereby electrical connections within said switch are closed when said cover is lifted, and opened when said cover is closed; an arm on said switch and a helical spring afllxed at one end to said arm. and at the other end to a rod passing through a lug; and a nut threaded to said rod whereby the tension of said spring may be adjusted to a value suflicient to prevent the lifting or said cover until the pressure of fluid within said valve exceeds the combined pressures exertggflby said s ring and by the steam within said MICHAEL C. CROTIY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,120,165 Tierney June 7, 1938 2,110,882 Knox Mar. 5, 1938 1,113,232 Mergott Oct. 13, 1914 961,434 Frampton June 14, 1910 2,296,426 Coutant Sept. 22, 1942 1,832,949 Strube Nov. 24, 1931 

